(1) Field of the Invention
The present invention relates to a textured composite yarn (core-wrapped composite yarn) having a spun yarn-like appearance and touch, and a process for the manufacture of the same.
(2) Description of the Prior Art
As disclosed in the specifications of U.S. Pat. No. 3,577,873 and No. 3,691,750, when at least two filamentary yarns differing in extensibility under stress are doubled, fed to a feed roller and twisted by a false twist element, the filamentary yarn having a lower extensibility occupies a core portion because of its reduced tendency to elongate, while the filamentary yarn having a higher extensibility is twisted to wrap the core portion helically because it is readily elongated. When this twisted state is thermally set and untwisting is thereafter effected, there is obtained a textured composite yarn having two layers, which yarn comprises a core portion mainly composed of the filamentary yarn having a lower extensibility and a wrapping portion composed of the filamentary yarn having a higher extensibility and helically wrapping the core portion in the twisted state.
Incidentally, by the term "yarn" used in the instant specification is meant a filamentary yarn unless otherwise indicated.
Such finished yarn is ordinarily manufactured at a processing speed lower than 100 m/min. However, to obtain a finished yarn of this type for use in making high quality woven or knitted fabrics, the yarn must be carefully prepared at a processing speed as low as 60 m/min or less. However, production at such a low speed tends to be very inefficient, thus disadvantageously causing the resultant product to be commercially unprofitable.
The reason why such a low processing speed must be adopted is because the stability of the specific structure inherent to an alternately twisted and wrapped yarn tends to be very poor and is not sufficiently high enough to withstand the false twisting (crimping) and weaving steps. Especially at the false twisting step, the composite yarn structure is more delicately changed in accordance with the speed of the texturing processing as compared with the structure of a filamentary yarn which is subjected to a texturing processing. More specifically, at a processing speed lower than 60 m/min, a uniform textured composite yarn structure comprising a core yarn and a yarn helically and alternately wrapping the core yarn in a twisted state can be obtained, and at a processing speed approximating to 100 m/min, a textured composite yarn structure wherein the wrapping by the filamentary yarn is partially incomplete and non-uniform will inevitably be obtained. However, at a processing speed of 150 to 250 m/min, the wrapped structure is manifested at a few locations, and at a processing speed exceeding 300 m/min, no wrapped structure is formed and only a crimped yarn composed of two completely separate yarns can be obtained.
Namely, the configuration of the two-layer textured composite yarn is changed to that of a textured yarn produced by a twisting-untwisting method or false-twisting method, as the processing speed is increased, and the quality of a woven or knitted fabric formed from a yarn manufactured at a high processing speed is degraded, that is, the spun yarn-like appearance or touch is drastically degraded. Further, in the portion having no wrapped structure, slacks corresponding to the difference between the extensibility of the core yarn and that of the wrapping yarn are created in the wrapping yarn, thereby forming neps in the winding zone during the false twisting step or during the weaving step. Finally, serious defects such as troubles occurring during operation and drastic reduction of the quality of the final product will be caused by the neps formed in the yarn.
In the above-mentioned slackened portion, filaments are present substantially in a free state, and even if a woven or knitted fabric can be formed from a yarn having such slackened portions, the anti-pilling property is extremely poor and the product is not fit for long-time wearing. Accordingly, various defects will be caused during actual application of such product.